Electrolytic apparatus for the recovery of metals



Aug. 4, 1942. N. B. AUKER'MAN ELECTROLYTIC APPARATUS FOR THE RECOVERY OF METALS Fild April 4, 1939 \\\\\\\V.A\\\\\\\\\\\\\\\\\\\\\\\\Y lNvENToR Qmm ' TTORNEY l Patented Aug'. 4, 1942 tion. More particularly; inventionf relates to the'recovery o f silverlfrom photographicsolutions and is :directed newland useful-improvements in l'apparatus of .the type A.discloflier-lem Kmyx- 1 that the silver ordinarily lostfin y the developing vrecovered 'simply aridinexpensivelyby maintain 5; ing a suitably designed electrocouple immersed in thephotographidbathgf By the electrochemical action of the `electrolytes'in such `baths on: the

copper and zinc elements'bi-the electrocouple a low voltage potential lWasflriuilgt up whichcaused n depositionof silverfonthe. errposedfsuriaces of the copper elements. "I havefoundihowever, vthat-the arrangementfof the" copprand zinc; elements `in this unit results in a device that-is :relatively'inefficient and moreover' has 'a' deleterious .effect en the'photo'graphic'bath. Y Thus I have found that with-the, zinc strips arranged atwise withthe edges incontact with two similarly arranged copperstrips, as shown in my prior patent; the zincfdisintegrates most rapidly at the line .of contact with the copper and hasthe eiect' 'of gradually separating the zinc from thecopper. The unitathereiore, have a high initial potential 'which gradually drops o!! in proportion to the disintegration of thezinc f along the-edges adjacent` the' copper so thai-.the unit becomes less and vlesseilic'ient they longer it is allowed Vto remain irl the photographic .batln Moreover, I' have observed that 'they high initial potential so formed-[may inmany cases be soA high as to causeidismte'gration of *thetath with the iormation of an undesirable: sludge which makes the bathunsafe to use,. Also I have 1ound that the deposit obtain ed .lack`s cohesiveness and tends to rumme'in thebath' making it dimcult torecover the silver as a compact'mass'.; y

Now, this invention is particularly overcoming these dsadvantagesandhas for, an object thel provision of. a. more ellcien tunitl which by virtue of its increased emciency v.may be madesmaHer'and thereby better suited -toruse in comercial photographic tanks, A further.

object is t"o obtain amore uniform rate' o t depositiorrV hroughoutijthe vlife "of'fthe unit." A" 'still furtherfob'ject '.-Iisito prevent f' disintegration 'and fsludgingfin 1-thebath1v -An'other objectl is, to .o b- 1- .tai-n a more; cohesivelarid more easily recoverable .wstantially: as illustrated-fin 1 the accompanying plates assembled" in face-"toiface relation' to form' .failstackfeachof Awhich 4is separated from 4the zinc plates I', 315y1and1 as forminganother negative `elementl which forms an electrocouple y with the ypositive copper plateV 19. "Whilefthere 1s some coupling between copper plate fand zinc plate 3f, it `is*relatively-1' small-'ascompared 'with 'the coupling betweencopperplate. 9 and 'aincjpla'te 3L @At least:one loffthe-positive plates should have a vfree' surfaceexposed to thejlsolution 'to provide, amlating sur-face onwhich' thejmet'alls del posited; :that is-tovsay; it thciuld'have but one of 40 its faces :adjacentafzmcplateL' Each copper' plate s houldfform a couple-with atleastv twozinc plates prg. more simply," none of f the vzinc plates'f shouldnhave-.vboth `faces-"adjacent a copper plate." Thus za. copper 'plate` may be locateciat either orgboth sides of-'alplurality of -zinc "p1ates'. It

extended beyond the zinc plates toform a plating surface asiand for, the purpose' presently to be ..I have found that-the greater the areaoi pp slf' tive plate exposed =freely Vto the electrolytic 'soluf tlonthe more cohesive isthe deposit;v Thus bet- L ter to'obtain-a more compact- Aand easily`recover` able deposit I'increaselthesurface area of copper and l1. A thin brass sheet Il), suitably about 36 that the apparatus .described is not means of. the brass covering I; II;` thisbrass`l` alone. itis` preferable torinclose. It in an insulatcovering I0 contactscopper plate 9 asv-illustrated. ing casing as shown.v in. Figure .1', especially if at II or is closely adjacent theretoit willL as-.. the'photographictankis'made'of metal. Qthersume the potential of the positive element so that wise they silverf lrlayy be deposited. on the exposed reduction ofthe silver ions will'take place on thef 5.; surfaces of thetank which either by contact or surface of plate I0; This brass plate I0 is wrap` close proximityfto thepositive plating surface I0 pecl around the stacked copper andl zinc. ele-V will: assume the saine,v 1o w potential. As. illusmentstoform a casing therefor. trated; the-fcasingl:is; made'in the form of an I have found'` also vthat Idisintegration of. the open-sidedbox;soastoprovide free accessof -the zinc elements is more intensev the closer the.- v electrolytetothe platingzsurtacell. Wood, suitcouple betweenv the zinc and .copperand thatfthisfably; Waterprooied: with. Paraninor other matecan be avoided by maintaining a proper-v spacing,v rial; has',.beenrfoundzentirely-suitable as an insubetween the zinc elements so that the electrolyte'.y 'laton Bymakinzgthe-copper'plate Honger than is more freely accessible to .the zincelements.:` the.:zinoplatestthekcoreA- may. be simplyami more remote from the copper. Thus asfillus-v eiectivelysecuredlin'-the;casing sfillustrated at trated in Figure 2, the spacing between any` two Isa. remote plates (for example, zinc plates I andZ'., The Casing Bf may be' made. t0 form still i or 2 and 4`). is greater than the spacinglletweenv further" function. namely: that 0f prOVidinZ 8 any two zinc plates less remotev (for example,l supportforadditionalgplating surface. 'I'hus the zinc. plates 2 and 4, or 4 and 6). This; permits 20 topboard-y 2.0i asf. illustrated in` Figure 2- may be the electrolyte to circulate more freely between covered. with a brass sheet ZI which serves as the zinc plates` more remote from theV copper an extensionottheplating surfacelll.l This sheet plates and, thus compensates for the greater-dislikewiseis.v coveredwith` nettingv as shown at 22 tance between the copper and zinc plates. to.v provide forv improved adherence of the de- This construction and arrangement of the core y positedi'silver; Itr is4 not necessary t0 have the A maybe better understood byl reference to the` brass sheetyZ'Il contacttheY brass sheet I 0 since following description of thev manner inzwhich itv though two layersA ofV netting; separatethe two is assembled. The zinc plate `I is wrapped in a plates the electrolyte forms. anV adequater elecsmall piece of het fabric I2 suflicient toprovide; trical. connection; between. the two plates. By two layersoflnetting on each side. So wrapped. this arrangement" I"P10Vide an. effective. Plating it is placedy on: a` second strip of nety fabric4 I3.- surface ranging-fromato'b.- b to C. cto d, d to e, about threewidths off the plate from the endV Il. et0 f; f: t0A ypand g. to. h on which the sil'ver The free end Ilofthe netting cloth is folded'over builds up over,u the tOD bOard 20'. 'I'his has the zinc plate I to provide three widths. of'netting advantageL of'causing; the silver to deposit away on` each side and to provide a double thickness 375; from the walls of the photographictank. For of netting of suijcient length to inclose. zinc example, it* the bOt'tOm board 23 iS. Placed adplates 2 and 3. With ,the successiveand apjacent a sidewall Qfnthe tankv or on the bottom propriate addition of; the remainingv plates the of the tank; thel silver deposits away from the remaining single thickness I5 of the nettingv is sidewallof thebottom` This avoids any possible wound around zinc plates 4, 5, etc. to. provide,- 40. short 'circuit which Would lead t0 depositiOn 0I single thicknesses between zinc plates 6. and l. silveronv the-wallsv ofthe tank'.

between zinc. plates, 5 and 1, between'- copper WhileI- hayegillustrated andrdescribed my inplate 8 and zinc plate 6, and between copper plate vention with reference to the recovery. of silver s and zinc plate 1. The wrapping is thenconfrom photographicjbaths andv with reference. to

tinued around copper plate 8 and copper plate! 45 particular materials of constructi on, namely to provideA the single thicknesses shown at I6 copper, zinc, an'd brass, it is to be understood .limited in gauge, is then laid on the remaining netting with any of these respects but that it may be used oneI edge underlying. copper plate 9 as illustrated for the recovery of lother metals from aqueOuS at Il. The two together, that is, the brass strip solutions of electrolyte;v that the `electrocouple andthe netting, are then wrapped around the may be formedl of metals other than copper and unit as shown and the free end. of the netting is zinc, certainy ofwhichhave been mentioned in folded under and retained by the free end of the myv prior patentV and others of which will be brass sheet as shown at I8. This gives. a unit readily apparent', to those skilled-in the art of in which the desired spacing between the zinc electrochemistry; and that other metal 0r alloys plates ismaintained thruout the active life of the may be usedto form a suitable plating Surface.

device byreason of the multiple wrapping of The platine surface should, of course. have netting and the inclosure in the brasscovering. a solution potential of thev samel order as that The unit thus` formed may be suspendedv ina of-r the positive, photographic tank and when so suspended willv couple. In order words,.b,oth the plating surface effect deposition of silver on the exposed surfaces andV the positive element of the electrocouple of the positivecovering I0. When so used it should be electropositive tothe negative element. serves two functions n that it prolongs the life Thus a plating surfaceA Lo1'- iron, lead, copper,- of the photographic bath andV reclaims vsilver nickel, etc. can be used in place; of brass. The therefrom which would otherwise be lost. 'I'he 65 latter, which isl the ordinary yellow brass of silver recovered averages' approximately .970 commerce, however, is readily available on the tine and requires. only melting for further useA openmarketinfthe form ofthin sheeting most in industry. The silver is not deposited as a suitable'for'the purposes ofjmy. invention. Moreplate. but rather as avthick uneven mass. It does overtbrass, being composed essentially of copper not, adhere strongly to the plating surfaceand 7o and-'zinc (about two-thirds copper and one-third may easily be removed. The covering of netting zinc)l introduces no; metals; which are not also over. the plating surface not only facilitates its introduced by the elements ofthe electrocouple. removal but also aids in retaining the mass on I.claim:v

the plating surface. A 1. Apparatus-adapted to be immersedin and to vWhile the unit lust described may be employedy deposit metal' from. aqueous solutions. of elecelement (copper) ofthe electro;

trolytes comprising a couple formed of electronegative and electropositive plates assembled in face-to-face relation to form a stack containing atleast one unit composed of a plurality of said electronegative plates separated one from the other and from one of said electropositive plates by insulating means pervious to the solution of electrolyte, said unit being characterized in that the separation between any two adjacent electronegative platesV remote from the electropositive plate is greater than the separation between any other two adjacent electronegative 'plates less remote, andan electropositive metallickplating surface substantiallyenclosing said stack.

2. Apparatus adapted to be immersed in and to deposit metal from aqueous solutions of electrolytes comprising a couple formed of electronegative and electrcpositive plates assembled in face-to-face relation to form a stack containing at least one unit composed of two electrcpositive plates separated by a plurality of electronegative plates by insulating means pervious to the solution of the electrolyte, said unit being characterized in that the separation between any two adjacent electronegative plates remote from the nearest electropositive plate is greater than the separation between tronegative plates less remote from said last named electropositive plate, and an electr-opositive metallic plating surface substantially enclosing said stack. n

3. The apparatus of claim 2 in which the electropositive plates are copper, the electronegative plates are zinc, and the metallic plating surface is brass.

4. Apparatus adapted vto be immersed in and to deposit metal from aqueous solutions of. electrolytes comprising a couple formed of electronegative and electropositive plates assembled any other two adjacent elec-A A in face-to-face relation to form a stack containing at least one unit composed of two electropositive plates separated by a plurality of electronegative plates by insulating means pervious to the solution of the electrolyte, said unit being characterized in that the separation between any two adjacent electronegative plates remote from the nearest electropositive plate is greater than 'the separation between any other two adjacent electronegative plates less remote from 'said last named electropositive plate, and an electropositive metallic plating surface substantially enclosing said stack, said couple being enclosed in a housing composed of two parallel non-conducting members which project beyond said couple at least one of which is wrapped in an electropositive metallic plating surface.

5. The apparatus of claim' 4 in which the electropostive plates are :copper and the electronegative plates are zinc.

6. In apparatus for the recovery of metals from aqueous solutions of electrolytes, an immersion unit constructed and arranged to be activated by the electrolyte of the solution in which it is immersed comprising a couple formed of a plurality of electronegative 'and at least one electropositive plate assembled in face-to-face relation to form a stack and insulating means pervious to said electrolyte separating saidv plates and maintaining them out of direct electrical contact, and

Van electropositive metallic plating surfaceY substantially enclosing all the surfaces of electronegative plates exposed to said electrolyte and insulating means pervious to said electrolyte maintaining said metallic plating surface out of direct electrical contact with said electronegative plates, Y

NATHANIEL B.l AUKERMAN. 

